Hamatolenus (Myopsolenus) magnus Hupe 1953

This trilobite has a para-frontal band that is complete in front of the glabella (the para-frontal band is a continuation of the palpebral lobe).  I have moved the below specimen to this subgenus (from Hamatolenus) after further study partly because of Hupe's original description that the palpebral lobes of Myopsolenus reaches the posterior border of the cranidium, and Geyer's diagnosis that the palpebral lobes are more horizontally oriented on the cranidium as seen in his photos of type specimens of this genus.  It seems when looking at the right palpebral lobe that it does not reach the posterior border furrow but is broken off, and the left side though not preserved, the outline of where the lobe used to be seems to reach the posterior border.  Other defining characteristics are the shape and position of the palpebral lobes being distally away from the glabella along with the size of the glabella. 

 

The para-frontal band on this specimen can be traced almost all the way, one of the few where it is preserved enough to be seen.  Also the glabella is large, not pointed but round anteriorly. My observation after examining many similar trilobites that there are differences in glabellas that could be explained by the state it was preserved in, conceivably altering the appearance depending on this factor.  In instances where the glabella is not visible, or always the same appearance (for example, Kingaspis and Ornamentaspis) this would not be a factor, but for some Cambrian trilobites the glabella does not seem to be fixed in appearance one way or another; that is the actual preservation may alter the glabella's appearance depending on whether it is stout, "crushed" or slightly dinged in appearance.  This could alter the diagnoses of trilobites that are very similar in appearance otherwise.

Kenjiro 2015.5.29 (revised 2020.5.20)